As noted by the others if you have your wireless network security setup correctly there is no way unauthorized users will be able to access the network. FWIW here are my suggestions for home users that you may find of some interest...
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theillustratednetwork.mv ··· ity.htmlPersonally I use WPA2-PSK [AES] (aka WPA2-Personal) with a 63-character random ASCII key to protect my two wireless networks at home.
If your using a short encryption key/password/passphrase that is susceptable to dictionary type attacks then all bets are off...